When light passes through material such as glass, a portion of its energy is lost as it reflects off the material's surface. Researchers at Japan's Institute of Physical and Chemical Research (Riken) have come up with a theoretical design for preventing this phenomenon from occurring.

The researchers have designed a prism of engineered material -- metamaterial comprised of an arrangement of nano-coils of precious metals such as gold or silver -- embedded in a solid glass-like material. The prism structure has a negative refractive index, which makes it truly transparent to light, allowing it to pass freely through with no reflection.

In the future, this type of metamaterial prism could lead to improvements in low-loss fiber optic communications, the development of telescopes and cameras well-suited for dark subjects, and the emergence of optical equipment we have never seen before.

Nusco

Actually, I suspect that depends on whether the light gets refracted. If refraction is there, you should be able to see the "Predator effect" on an object made with this glass. At least until some nuclear physicist comes up and tells me that no reflection implicates no refraction, which is entirely possible AFAIK...

Bob Dole's penis

It's always about the hippies, isn't it? I guess being a hippie is better than being some limp-dick conservative that thinks they know everything.

By the way, birds already do that with normal glass. Frankly, I'm surprised anyone can get anything done with all the noise made by all the birds killing themselves by flying into glass windows and all the bitching by smelly hippies about all the glass everywhere killing poor little birdies. I can barely hear myself think with all the noise.

Larry

I agree wouldn't that truely make the glass invisible. Since all light is being fully passed through it, without one ounce of light being reflected (since that is how we see objects ). Just think of all birds hitting that frigin glass....

Zebov

No, it would not be invisible. As stated, the index of refraction would be negative. Unless the material has the same index of refraction as the surrounding medium (Air ~ 1) then it would NOT be invisible. Water is almost completely transparent but you can still see it in a glass. This is because of the index of refraction.

Scott

Nate

A negative index of refraction (to my understanding of physics) doesn't make any sense.
index of refration = (speed of light in a vacuum)/(speed of light in the object)
(n = c/vo)
So a negative index of refraction means that... light has a negative velocity inside of this substance?

Invisible? I don't know about that one, because even with 0 reflection (and I don't think this is going to be absolute 0 , but more like 0.001), you still have the property of light bending when it goes through a piece of glass. I think that effect will still reneder the glass 'visible' or at least 'detectable'.

Micah Fitch

Man, what a blatant misinterpretation. The negative index of refraction doesn't make it nonreflective! To my understanding it means that the light refracts as though it is bouncing off of the normal almost...

WeirdAdd

MaartenVdP

a index of refraction of 0 can only be achieved if the speed of light passing through the medium (the glass in this case) would be infinite. this involves infinite kinetic energy, via e=mc² this would meen you have an infinite mass...

now you see that invisible glass can't exist.
and an index of refraction below zero is, if possible, even more stupid.

KK

Birds hit regular glass because they see the sky reflected in it--this material, if it works as claimed, with no reflection, would prevent that, the birds would see the interior of the buildings and shy away. Hippies might run into it though, expecially if they are smoking stuff.

Calamier

I love the fact that you morons sit here and make all these skeptical comments and observations. You don't even think of anything like this on your own, you just nay-say when things like it do come around. Shut up.

Ryan

Replying to Nate's comment above about index of refraction less than one -

My take initially was that they actually meant an index of refraction less than one instead of it actually being negative. As you mentioned, a negative index of refraction would mean that either the speed of light in a vacuum or the speed of light in that substance has to be negative. That didn't seem right.

Unfortunately an index of refraction less than one doesn't work out either. According to Snells law, n1*sin(angle1) = n2*sin(angle2) (where angle1 is the angle of light entering the substance incident to the normal, n1 is that substances refractive index, angle2 is the angle again incident to the normal in material 2, and n2 is material 2's refractive index).

Knowing that n=1 for air, and lets just take this glass to have a refractive index of .5, with light entering the glass at a 45 degree angle, the equation is:

sin(45) = .5*sin(angle2)

Solving for angle two is "easy":

sin-1(sin(45)/.5) = undefined

The sin(45)/.5 is greater than one, and therefore not in the domain of the inverse sin function.

Can anyone explain what the negative index of refraction means in this case? Simple geometric optics doesn't seem to be able to describe where this value came from.

As far as can understand it means that light is refracted in 'unnatural' directions. i.e. light coming in at 45* from above would exit upwards at 45* the other side, an 'impossibility' under normal conditions. Sheesh, those crazy metamaterials!

Paul

I don't understand the importance of the index of refraction in this, could you explain?

I mean with the index of refraction, vacuum has 1.00000. The speed of light, travels at well, C in vacuum. And in a heavier medium such as water, its 1.333, and glass is 1.50. Then logically, wouldn't having an index of refraction lower than 1 mean that light in this material travels faster than in vacuum? Which is impossible.

John

qet

Some above have talked about the index of refraction and the lack of ability to be negative, which is mostly true. The definition of the index of refraction depends of the permitivity of free space and the magnetic permiability denoted epislon_0 and mu_0 respectively, and also on the phase velocity of the wave in question. Some materials exibit negative values for these at certain wavelengths (such as metals at visible wavelengths). This leads to a negative index of refraction. If this material has index of refraction about the same as air then you could not see it. What happens with negative index materials is that they behave oppositely of regular materials, so things like total internal reflection become total external reflection. normally if light hits a "converging" lens it converges, but if light hit a "converging" lens with a negative index material it would diverge instead. however this has nothing to do with it being invisible. there are many active research programs working on this type of stuff right now. here is a link to one of them

now back to the point, if it is gonna be invisible it has to have the same index of refraction as the medium it is being viewed in (in air ~1). as long as there is no frequency dependent scattering in the visible (which would make it appear to be a certain color) than it would be invisible and you could not see it. There would be no bending of light at the interfaces as ryan elegantly stated earlier with math.

You cant really analyze this with high school optics. Whats going on is that they have little coils that are aligned with the E and B fields of an electromagnetic wave. When the wave enters the material, it creates a current, creating a counter magnetic field which induces another current on the inner coil, which reinforces the original magnetic field.

the reason materials have slower speeds of light within the material is because its atoms are acting as a di-electric, absorbing some of the energy of an EM wave. this effectively eliminates the di-electric ness of the material.

Sci-fi references about force fields and predator-like appearances will never occur for the following reasons :

1. the light only has zero refractive index if it is incident on the coils exactly through the center. a simple statistical calulation will tell you that the amount of light that this occurs for approaches zero.

2. the light must be incident on the material parallel to all the coils. ( travelling transverse with respect to the surface of the material)

3. it seems that the coils are spaced exactly as the wavelength of a particular color of light, so that each sucessive electric and magnetic field wavefront will peak at each coil.

4. there has to be no phase shift, for example if the EM wave was exactly half a wavelength off, there would be nearly no effect.

so there is only zero refractive index if 1. you shine an extremely narrow beamed laser. 2. at the exact specified wavelength 3. at the exact angle and polarization. 4. in exactly the plane of the surface material. 5. at the exact amount of phase shift (you might have to move the laser back and forth +/- lambda to fix the right position)

which yes, would be practical for perfectly straight optic fibers driven by coherent lasers.

tryforceful

Joozie

I say simply max respect to Ryan ^_^
before trying with your only knowledge to find a fault in a theory of highests Japanese engeneers, try first to learn a little competence to understand what they have said. ^_^ And wikipedia is always the right place.
Not only "high school optics" can understand such technology: do you really think that with only a fresh degree in Phisics at MIT you can understand the TOP OF THE TOP researchers in Japan? At least, try to find first a more explicative article on which they talk about their discover!! Or wiki-it! ^_^
Nice one Ryan!! :D

Davin Wood

Joe cool

Hold up... Invisible glass? That IS the catch. Have you all forgotten that nitrogen and oxygen are NOT invisible. Special equipment, or possibly even some well-trained eyesight could notice this stuff, it would look like a vacuum moving through our atmosphere. HAH!

Jun Feng

xmarmite

If this is 100% transparent then light would pass through this material without any effect… it would not refract!!! If light is not affected then how on earth could you create a “lens” out of this material? If you cannot create a lens then you cannot create an optical instrument.

Also Fibre Optics rely on “total internal reflection” in a material not transparency.....or am I just missing something.

What a metaphoric picture of loss we suffer in our when our vision is marred by negativity of any sort.... This post really inspires another look at reflection we each bring to our day! Thanks for the wonderful description...

George

I couldn't understand some parts of this article ugh the (zero-reflection) looking glass ::: Pink Tentacle, but I guess I just need to check some more resources regarding this, because it sounds interesting.

Billybob Frob

Aaron

Physicist Amateur Hour! Assumption: Changing momentum or speed (refraction) will require energy to be put into or taken out of the system. So if the data shows that no energy is lost, there can't be any refraction.